7 research outputs found
Spectral disentangling with Spectangular
The paper introduces the software Spectangular for spectral disentangling via
singular value decomposition with global optimisation of the orbital parameters
of the stellar system or radial velocities of the individual observations. We
will describe the procedure and the different options implemented in our
program. Furthermore, we will demonstrate the performance and the applicability
using tests on artificial data. Additionally, we use high-resolution spectra of
Capella to demonstrate the performance of our code on real-world data. The
novelty of this package is the implemented global optimisation algorithm and
the graphical user interface (GUI) for ease of use. We have implemented the
code to tackle SB1 and SB2 systems with the option of also dealing with
telluric (static) lines
Spectangular: Disentangling variable spectra
Spectangular is a GUI based software package written in C++ designed for
spectral disentangling on the wavelength scale. The code disentangles spectra
of SB1 and SB2 systems and can now also be used also for spectra showing
variability. In this work, effects of variability caused by telluric lines,
line profile, and continuum flux are being investigated. Also shown is the
disentangling on spectra from an artificial eclipsing binary. It is now
possible to optimize on the flux ratios of each spectrum, making the
disentangling a technique for extracting photometric information from
spectroscopic observations usually provided by additional photometry.
Furthermore, we make some comments about changes to the code since it was first
published.Comment: accepted to A&
Carbon 12C/13C isotope ratio of alpha Aurigae revised
Context. Capella ({\alpha} Aur) is one of the few binaries in the sky with
two cool giant stars. With spectral types of G8III and G0III, the two
components appear at different but distinct stages in their evolution. The G0
secondary star is a Hertzsprung-gap giant, and the G8 primary star is thought
to be a clump giant. Aims. We present a new measure of the carbon 12 C/ 13 C
isotope ratio of the primary component of Capella using high-resolution R
250 000 spectra obtained with the Potsdam Echelle Polarimetric and
Spectroscopic Instrument (PEPSI) with both the Vatican Advanced Technology
Telescope (VATT) and the Large Binocular Telescope (LBT). Methods.
Signal-to-noise ratios of up to 2 700 were obtained by averaging nightly
spectra. These average spectra were used to disentangle the two binary
components. The isotope ratio was derived with the use of spectrum synthesis
from the CN lines at 8004 {\AA}. Results. We found that the 12 C/ 13 C ratio of
the primary component of Capella is 17.81.9. Our measurement precision is
now primarily limited by the spectral-line data and by the grid-step size of
the model atmospheres rather than the data. The separated spectrum of the
secondary component does not show distinguishable 12 CN and 13 CN lines because
of its v sin i and higher temperature. Conclusions. Our new 12 C/ 13 C value is
significantly lower than the previous value of 274 but now agrees better
with the recent model prediction of 18.8 - 20.7.Comment: accepted to A&A Letters to the Edito